U.S. patent application number 17/133737 was filed with the patent office on 2021-04-22 for person support apparatuses with load cells.
The applicant listed for this patent is Stryker Corporation. Invention is credited to Jonathan Mark Greenbank, Marko N. Kostic, Sujay Sukumaran.
Application Number | 20210113401 17/133737 |
Document ID | / |
Family ID | 1000005305630 |
Filed Date | 2021-04-22 |
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United States Patent
Application |
20210113401 |
Kind Code |
A1 |
Kostic; Marko N. ; et
al. |
April 22, 2021 |
PERSON SUPPORT APPARATUSES WITH LOAD CELLS
Abstract
A person support apparatus, such as a bed, cot, stretcher,
chair, or the like, includes a frame, a support surface supported
by the frame, a plurality of load cells that detect weight
supported on the support surface, at least one A/D converter, and a
controller. The load cells output analog signals that are converted
to digital by the A/D converters. The controller switches a
sampling rate of the A/D converters between at least first and
second rates. The outputs from the load cells are forwarded to a
plurality of signal acquisition nodes that include the A/D
converters. The nodes are positioned at locations that minimize the
length of travel of the analog signals, thereby reducing noise
interference. Shivering, occupant absence/presence, vital signs,
occupant movement, and/or other parameters are detected by the load
cells.
Inventors: |
Kostic; Marko N.; (Oshawa,
CA) ; Sukumaran; Sujay; (Portage, MI) ;
Greenbank; Jonathan Mark; (Plainwell, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Stryker Corporation |
Kalamazoo |
MI |
US |
|
|
Family ID: |
1000005305630 |
Appl. No.: |
17/133737 |
Filed: |
December 24, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15826779 |
Nov 30, 2017 |
10898400 |
|
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17133737 |
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62428834 |
Dec 1, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61G 7/0527 20161101;
A61B 5/11 20130101; A61G 2203/44 20130101; A61G 7/015 20130101;
A61G 7/018 20130101; A61G 7/012 20130101 |
International
Class: |
A61G 7/05 20060101
A61G007/05 |
Claims
1. A person support apparatus comprising: a frame; a plurality of
load cells supported by the frame, each of the plurality of load
cells adapted to output analog signals indicative of loads detected
by the load cells; a support surface adapted to support thereon an
occupant of the person support apparatus, the support surface being
supported by the load cells such that a weight of the occupant is
detectable by the load cells when the occupant is positioned on the
support surface; an analog-to-digital converter adapted to convert
analog signals from at least one of the load cells into digital
signals at a first rate; and a controller adapted to analyze the
digital signals from the analog-to-digital converter to determine
when the occupant supported on the support surface is
shivering.
2. The person support apparatus of claim 1 wherein the
analog-to-digital converter is further adapted to convert the
analog signals from at least one of the load cells into the digital
signals at a second rate slower than the first rate, and the
controller is further adapted to analyze the digital signals from
the analog-to-digital converter to determine when the occupant is
shivering when the analog-to-digital converter is operating at the
first rate but not when operating at the second rate.
3. The person support apparatus of claim 1 wherein the plurality of
load cells are part of an exit detection system adapted to detect
when the occupant of the person support apparatus exits
therefrom.
4. The person support apparatus of claim 3 wherein the controller
is further adapted to transmit an exit detection message off of the
person support apparatus to an off-board device when the occupant
exits.
5. The person support apparatus of claim 3 wherein the controller
is further adapted to transmit a shivering message off of the
person support apparatus to an off-board device when the controller
detects the occupant is shivering.
6. The person support apparatus of claim 5 wherein the off-board
device is a thermal control unit adapted to control a temperature
of the occupant.
7. The person support apparatus of claim 2 wherein the controller
is further adapted to switch between the first rate and the second
rate based upon the digital signals from the analog-to-digital
converter.
8. The person support apparatus of claim 2 wherein the controller
is adapted to switch to the first rate when a change above a
threshold amount occurs in the digital signals from the at least
one of the load cells.
9. The person support apparatus of claim 8 wherein the controller
is adapted to switch to the second rate when changes above the
threshold amount are not detected for a threshold time in the
digital signals from the at least one of the load cells.
10. The person support apparatus of claim 8 wherein the controller
is adapted to determine the weight of the occupant when the
analog-to-digital converter is operating at the second rate, and
wherein the controller is further adapted to automatically
determine a tare weight before the occupant enters the support
surface.
11. A person support apparatus comprising: a frame; a plurality of
load cells supported by the frame, each of the load cells adapted
to output analog signals indicative of loads detected by the load
cells; a support surface adapted to support thereon an occupant of
the person support apparatus, the support surface being supported
by the load cells such that a weight of the occupant is detectable
by the load cells when the occupant is positioned on the support
surface; a first signal acquisition node comprising a first
analog-to-digital converter adapted to convert analog signals from
a first one of the load cells into digital signals; a second signal
acquisition node spaced away from the first signal acquisition
node, the second signal acquisition node comprising a second
analog-to-digital converter adapted to convert analog signals from
a second one of the load cells into digital signals; and a
controller spaced from the first and second signal acquisition
nodes, the controller communicatively coupled to the first and
second signal acquisition nodes and adapted to determine a weight
supported on the support surface based upon the digital signals
from the first and second signal acquisition nodes, the controller
further adapted to analyze the digital signals from the first and
second signal acquisition nodes to determine when the occupant
supported on the support surface is shivering.
12. The person support apparatus of claim 11 wherein the plurality
of load cells are part of an exit detection system adapted to
detect when the occupant of the person support apparatus exits
therefrom.
13. The person support apparatus of claim 12 wherein the controller
is further adapted to transmit an exit detection message off of the
person support apparatus to an off-board device when the occupant
exits.
14. The person support apparatus of claim 11 wherein the controller
is further adapted to transmit a shivering message off of the
person support apparatus to an off-board device when the controller
detects the occupant is shivering.
15. The person support apparatus of claim 14 wherein the off-board
device is a thermal control unit adapted to control a temperature
of the occupant.
16. The person support apparatus of claim 11 wherein the first
signal acquisition node sends the digital signals from the first
analog-to-digital converter to the second signal acquisition node,
and the second signal acquisition node sends the digital signals
from both the first and second analog-to-digital converters to the
controller.
17. The person support apparatus of claim 11 wherein the first
signal acquisition node and the first one of the load cells are
both positioned adjacent a head end of the person support
apparatus, and the second signal acquisition node and the second
one of the load cells are both positioned adjacent a foot end of
the person support apparatus.
18. The person support apparatus of claim 11 wherein the controller
is adapted to automatically determine a tare weight of the support
surface based on the digital signals from the first and second
signal acquisition nodes, the controller adapted to automatically
determine the tare weight before the occupant enters the support
surface.
19. The person support apparatus of claim 11 wherein both the first
and second analog-to-digital converters are adapted to operate at a
first rate and at a second rate, and wherein the controller is
adapted to instruct the first and second analog-to-digital
converters which of the first and second rates to operate at.
20. The person support apparatus of claim 11 wherein both the first
and second analog-to-digital converters are adapted to operate at a
first rate and at a second rate; the first signal acquisition node
includes first processing circuitry adapted to analyze the digital
signals from the first analog-to-digital converter to determine
whether to operate the first analog-to-digital converter at the
first rate or the second rate; and the second signal acquisition
node includes second processing circuitry adapted to analyze the
digital signals from the second analog-to-digital converter to
determine whether to operate the second analog-to-digital converter
at the first rate or the second rate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. patent application
Ser. No. 15/826,779 filed Nov. 30, 2017, by inventors Marko Kostic
et al. and entitled PERSON SUPPORT APPARATUSES WITH LOAD CELLS,
which in turn claims priority to U.S. provisional patent
application Ser. No. 62/428,834 filed Dec. 1, 2016, by inventors
Marko Kostic et al. and entitled PERSON SUPPORT APPARATUSES WITH
LOAD CELLS, the complete disclosures of both of which are
incorporated herein by reference.
BACKGROUND
[0002] The present disclosure relates to person support
apparatuses, such as beds, cots, stretchers, operating tables,
recliners, or the like. More specifically, the present disclosure
relates to person support apparatuses that include load cells.
[0003] Existing hospital beds and/or stretchers often include a
load cell system that is used to detect the weight of an occupant
of the bed or stretcher, and/or that is used as an exit detection
system. When functioning as a scale system, the outputs of the load
cells are read and a weight of the occupant is detected. When
functioning as an exit detection system, the outputs of the load
cells are read and used to detect when a patient has exited the bed
or stretcher, or when a patient may be about to exit the bed or
stretcher.
SUMMARY
[0004] According to various embodiments, the present disclosure
provides a person support apparatus having an improved load cell
system that is configured to provide more accurate results. In some
embodiments, the person support apparatus includes load cells whose
outputs are better shielded from Electromagnetic Interference
(EMI). The person support apparatus may also or alternatively
include analog-to-digital converters that operate at multiple
sampling rates whereby the sampling rates are automatically
controlled based on one or more conditions. In some embodiments,
the load cells are used to monitor and log the times at which a
person has been on the person support apparatus and the times at
which the person has been out of the person support apparatus.
Automatic taring of the scale system may also or alternatively be
included.
[0005] According to one embodiment, a person support apparatus is
provided that includes a frame, a plurality of load cells, a
support surface, an analog-to-digital converter, and a controller.
The load cells are supported by the frame and adapted to output
analog signals indicative of loads detected by the load cells. The
support surface supports thereon an occupant of the person support
apparatus and is configured such that a weight of the occupant is
detectable by the load cells when the occupant is positioned on the
support surface. The analog-to-digital converter converts the
analog signals from at least one of the load cells into digital
signals at a first rate and at a second rate. The controller
switches the analog-to-digital converter between the first rate and
the second rate.
[0006] According to another embodiment, a person support apparatus
is provided that includes a frame, a plurality of load cells, a
support surface, a first signal acquisition node, a second signal
acquisition node, and a controller. The load cells are supported by
the frame and adapted to output analog signals indicative of loads
detected by the load cells. The support surface is adapted to
support thereon an occupant of the person support apparatus. The
support surface is supported by the load cells such that a weight
of the occupant is detectable by the load cells when the occupant
is positioned on the support surface. The first signal acquisition
node comprises a first analog-to-digital converter adapted to
convert analog signals from a first one of the load cells into
digital signals. The second signal acquisition node is spaced away
from the first signal acquisition node and comprises a second
analog-to-digital converter. The second analog-to-digital converter
converts analog signals from a second one of the load cells into
digital signals. The controller is spaced from the first and second
signal acquisition nodes and coupled thereto by wires. The
controller determines a weight supported on the support surface
based upon the digital signals from the first and second signal
acquisition nodes.
[0007] According to another embodiment, a person support apparatus
is provided that includes a frame, load cells, a support surface,
an analog-to-digital converter, and a controller. The load cells
are supported by the frame and adapted to output analog signals
indicative of loads detected by the load cells. The support surface
is adapted to support thereon an occupant of the person support
apparatus. The support surface is supported by the load cells such
that weight supported on the support surface is detectable by the
load cells. The analog-to-digital converter converts analog signals
from at least one of the load cells into digital signals at a first
rate and at a second rate. The controller detects when weight is
added and removed from the support surface and switches between the
first and second rates based on detecting added weight and removed
weight.
[0008] According to still another embodiment, a person support
apparatus is provided that includes a frame, a plurality of load
cells, a support surface, and a controller. The load cells are
supported by the frame and are each adapted to output analog
signals indicative of loads detected by the load cells. The support
surface is adapted to support thereon an occupant of the person
support apparatus. The support surface is supported by the load
cells such that weight supported on the support surface is
detectable by the load cells. The controller uses outputs from the
load cells to detect and record an entry time when the occupant
enters the person support apparatus and to detect and record an
exit time when the occupant exits the person support apparatus.
[0009] According to other aspects, the controller switches between
the first and second rates of the analog-to-digital converters
based upon the digital signals output from the analog-to-digital
converters.
[0010] In some embodiments, the first rate is more than one hundred
times as fast as the second rate.
[0011] The controller is adapted to switch from a slow rate to a
fast rate, in some embodiments, whenever a change above a threshold
amount occurs in the digital signals from an analog-to-digital
converter. Alternatively, or additionally, the controller is
adapted to switch to the slow rate when changes above the threshold
amount are not detected for a threshold time in the digital
signals.
[0012] The controller uses the digital signals from the at least
one of the load cells to determine a weight of the occupant in some
embodiments. When doing so, the controller determines the weight of
the occupant when the analog-to-digital converter is operating at
the slow rate.
[0013] The controller is programmed, in some embodiments, to
automatically determine a tare weight before the occupant enters
the support surface.
[0014] In some embodiments, the controller uses the digital signals
from the load cells to determine when the occupant enters the
person support apparatus and when the occupant exits the person
support apparatus. The controller also records an entry time when
the occupant enters the person support apparatus and an exit time
when the occupant exits the person support apparatus. The
controller is adapted to display the entry time and exit time on a
display of the person support apparatus. In some embodiments, the
person support also includes a transceiver adapted to communicate
with an off-board device, and the controller transmits the entry
time and exit time to the off-board device.
[0015] In some embodiments, the first signal acquisition node sends
the digital signals from the first analog-to-digital converter to
the second signal acquisition node, and the second signal
acquisition node sends the digital signals from both the first and
second analog-to-digital converters to the controller. The first
signal acquisition node and the first one of the load cells are
both positioned adjacent a head end of the person support
apparatus, in at least one embodiment. In such embodiments, the
second signal acquisition node and the second one of the load cells
are both positioned adjacent a foot end of the person support
apparatus.
[0016] In some aspects of the disclosure, the first and second
signal acquisition nodes include first and second filters adapted
to filter out frequencies above a threshold in the analog signals
from the load cells.
[0017] The first signal acquisition node may include first
processing circuitry adapted to analyze the digital signals from
the first analog-to-digital converter to determine whether to
operate the first analog-to-digital converter at the first rate or
the second rate. In such embodiments, the second signal acquisition
node includes second processing circuitry adapted to analyze the
digital signals from the second analog-to-digital converter to
determine whether to operate the second analog-to-digital converter
at the first rate or the second rate.
[0018] According to other aspects, the controller is configured to
automatically distinguish between weight changes resulting from the
occupant entering or exiting the person support apparatus and
weight changes resulting from objects added to or removed from the
person support apparatus.
[0019] The load cells may be part of an exit detection system
having an armed state in which the controller issues an alert when
the occupant exits the person support apparatus and a disarmed
state in which the controller does not issue an alert when the
occupant exits the person support apparatus. In such embodiments,
the controller detects when weight is added and removed from the
support surface when the exit detection system is in both the armed
state and the disarmed state. The controller may be further adapted
to automatically change the exit detection system to the armed
state after the occupant enters the person support apparatus.
[0020] In some embodiments, the person support apparatus includes
at least four load cells.
[0021] In any of the person support apparatuses described herein,
the person support apparatus may be one of a bed, a recliner, a
cot, and a stretcher.
[0022] Before the various embodiments disclosed herein are
explained in detail, it is to be understood that the claims are not
to be limited to the details of operation or to the details of
construction and the arrangement of the components set forth in the
following description or illustrated in the drawings. The
embodiments described herein are capable of being practiced or
being carried out in alternative ways not expressly disclosed
herein. Also, it is to be understood that the phraseology and
terminology used herein are for the purpose of description and
should not be regarded as limiting. The use of "including" and
"comprising" and variations thereof is meant to encompass the items
listed thereafter and equivalents thereof as well as additional
items and equivalents thereof. Further, enumeration may be used in
the description of various embodiments. Unless otherwise expressly
stated, the use of enumeration should not be construed as limiting
the claims to any specific order or number of components. Nor
should the use of enumeration be construed as excluding from the
scope of the claims any additional steps or components that might
be combined with or into the enumerated steps or components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a perspective view of a person support apparatus
according to a first embodiment;
[0024] FIG. 2 is a perspective view of a litter and a pair of lift
header assemblies with load cells of the person support apparatus
of FIG. 1;
[0025] FIG. 3 is a perspective view of a base of the person support
apparatus of FIG. 1;
[0026] FIG. 4 is a plan view block diagram of a load cell system
incorporated into a person support apparatus, such as the person
support apparatus of FIG. 1;
[0027] FIG. 5 is a detailed block diagram of a signal acquisition
node of the load cell system of FIG. 4;
[0028] FIG. 6 is a block diagram of an alternative load cell system
that may be incorporated into the person support apparatus of FIG.
1, as well as other person support apparatuses;
[0029] FIG. 7 is a block diagram of yet another alternative load
cell system that may be incorporated into the person support
apparatus of FIG. 1, as well as other person support
apparatuses;
[0030] FIG. 8 is a graph of an illustrative gross weight output
from the load cell systems disclosed herein illustrating a manner
of auto-zeroing a scale system; and
[0031] FIG. 9 is another graph of an illustrative gross weight
output from the load cell systems disclosed herein illustrating
another manner of auto-zeroing a scale system when the scale system
has already detected an object.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0032] An illustrative person support apparatus 20 according to a
first embodiment is shown in FIG. 1. Although the particular form
of person support apparatus 20 illustrated in FIG. 1 is a bed
adapted for use in a hospital or other medical setting, it will be
understood that person support apparatus 20 could, in different
embodiments, be a cot, a stretcher, a gurney, a recliner, an
operating table, a residential bed, or any other structure capable
of supporting a person, whether stationary or mobile and/or whether
medical or residential.
[0033] In general, person support apparatus 20 includes a base 22
having a plurality of wheels 24, a pair of lifts 26 supported on
the base, a litter frame 28 supported on the lifts 26, and a
support deck 30 supported on the litter frame 28. Person support
apparatus 20 further includes a footboard 34 and a plurality of
siderails 36. Siderails 36 are all shown in a raised position in
FIG. 1 but are each individually movable to a lower position in
which ingress into, and egress out of, person support apparatus 20
is not obstructed by the lowered siderails 36.
[0034] Lifts 26 are adapted to raise and lower litter frame 28 with
respect to base 22. Lifts 26 may be hydraulic actuators, pneumatic
actuators, electric actuators, or any other suitable device for
raising and lowering litter frame 28 with respect to base 22. In
the illustrated embodiment, lifts 26 are operable independently so
that the tilting of litter frame 28 with respect to base 22 can
also be adjusted. That is, litter frame 28 includes a head end 38
and a foot end 40, each of whose height can be independently
adjusted by the nearest lift 26. Person support apparatus 20 is
designed so that when an occupant lies thereon, his or her head
will be positioned adjacent head end 38 and his or her feet will be
positioned adjacent foot end 40.
[0035] Litter frame 28 provides a structure for supporting support
deck 30, footboard 34, and siderails 36. Support deck 30 provides a
support surface for a mattress (not shown in FIG. 1), or other soft
cushion, so that a person may lie and/or sit thereon. The top
surface of the mattress or other cushion forms a support surface
for the occupant. Support deck 30 is made of a plurality of
sections, some of which are pivotable about generally horizontal
pivot axes. In the embodiment shown in FIG. 1, support deck 30
includes a head section 42, a seat section 44, a thigh section 46,
and a foot section 48. Head section 42, which is also sometimes
referred to as a Fowler section, is pivotable about a generally
horizontal pivot axis between a generally horizontal orientation
(not shown in FIG. 1) and a plurality of raised positions (one of
which is shown in FIG. 1). Thigh section 46 and foot section 48 may
also be pivotable about generally horizontal pivot axes.
[0036] FIG. 2 illustrates in greater detail litter frame 28
separated from lifts 26 and base 22. Litter frame 28 is also shown
in FIG. 2 with support deck 30 removed. Litter frame 28 is
supported by two lift header assemblies 50. A first one of the lift
header assemblies 50 is coupled to a top 32 (FIG. 3) of a first one
of the lifts 26, and a second one of the lift header assemblies 50
is coupled to the top 32 of the second one of the lifts 26. Each
lift header assembly 50 includes a pair of load cells 52. The
illustrated embodiment of person support apparatus 20 therefore
includes a total of four load cells 52, although it will be
understood by those skilled in the art that different numbers of
load cells may be used in accordance with the principles of the
present disclosure. Load cells 52 are configured to support litter
frame 28. More specifically, load cells 52 are configured such that
they provide complete and exclusive mechanical support for litter
frame 28 and all of the components that are supported on litter
frame 28 (e.g. support deck 30, footboard 34, siderails 36, etc.).
Because of this construction, load cells 52 are adapted to detect
the weight of not only those components of person support apparatus
20 that are supported by litter frame 28 (including litter frame 28
itself), but also any objects or persons who are wholly or
partially being supported by support deck 30.
[0037] The mechanical construction of person support apparatus 20,
as shown in FIGS. 1-3, is the same as, or nearly the same as, the
mechanical construction of the Model 3002 S3 bed manufactured and
sold by Stryker Corporation of Kalamazoo, Michigan. This mechanical
construction is described in greater detail in the Stryker
Maintenance Manual for the MedSurg Bed, Model 3002 S3, published in
2010 by Stryker Corporation of Kalamazoo, Mich., the complete
disclosure of which is incorporated herein by reference. It will be
understood by those skilled in the art that person support
apparatus 20 can be designed with other types of mechanical
constructions, such as, but not limited to, those described in
commonly assigned, U.S. Pat. No. 7,690,059 issued to Lemire et al.,
and entitled HOSPITAL BED; and/or commonly assigned U.S. Pat.
publication No. 2007/0163045 filed by Becker et al. and entitled
PATIENT HANDLING DEVICE INCLUDING LOCAL STATUS INDICATION,
ONE-TOUCH FOWLER ANGLE ADJUSTMENT, AND POWER-ON ALARM
CONFIGURATION, the complete disclosures of both of which are also
hereby incorporated herein by reference. The mechanical
construction of person support apparatus 20 may also take on forms
different from what is disclosed in the aforementioned
references.
[0038] Load cells 52 are part of a load cell system 54 (FIG. 4).
Load cell system 54 includes, in addition to load cells 52, a first
signal acquisition node 56a, a second signal acquisition node 56b,
a controller 58, a communications module 60, and a control panel
62. Load cell system 54 functions as a scale system, an exit
detection system, and/or an occupant monitoring system. When
functioning as a scale system, load cell system 54 is adapted to
measure the amount of weight that is supported on litter frame 28.
Through the use of an automatic taring function described in more
detail below, the weight of the litter frame 28 and other
components of the person support apparatus 20 can be separated from
the weight reading such that a weight of just the occupant of
person support apparatus 20 can be determined.
[0039] When load cell system 54 functions as an exit detection
system, load cell system 54 is adapted to determine when an
occupant of person support apparatus 20 has left, or is likely to
leave, person support apparatus 20, and to issue an alert and/or
notification to appropriate personnel so that proper steps can be
taken in response to the occupant's departure (or imminent
departure) in a timely fashion. In at least one embodiment, load
cell system 54 acts as an exit detection system by monitoring the
distribution of mass or center of gravity of the patient using the
system and method disclosed in commonly assigned U.S. Pat. No.
5,276,432 issued to Travis and entitled PATIENT EXIT DETECTION
MECHANISM FOR HOSPITAL BED, the complete disclosure of which is
incorporated herein by reference. Other manners for functioning as
an exit detection system are also possible. Further, in some
embodiments, load cell system 54 functions both as an exit
detection system and as a scale system.
[0040] When operating as an occupant monitoring system, load cell
system 54 is adapted to monitor movement of the occupant of person
support apparatus 20, including keeping track of when the occupant
enters and leaves person support apparatus 20, when objects are
added to and/or removed from person support apparatus 20. In some
embodiments, load cell system 54 may also or alternatively monitor
one or more vital signs of the occupant, detect shivering of the
occupant, and/or perform other occupant monitoring functions. When
monitoring occupant movement, load cell system 54 may be configured
to monitor such movement based on changes in the occupant's center
of gravity or mass distribution, or on other factors. In at least
one embodiment, load cell system 54 acts as an occupant monitoring
system in any of the manners disclosed in commonly assigned U.S.
patent application Ser. No. 14/873,734 filed Oct. 2, 2015, by
inventors Marko Kostic et al. and entitled PERSON SUPPORT APPARATUS
WITH MOTION MONITORING; and/or commonly assigned U.S. patent
publication 2016/0022218 filed Mar. 13, 2014, by inventors Michael
Hayes et al. and entitled PATIENT SUPPORT APPARATUS WITH PATIENT
INFORMATION SENSORS, the complete disclosures of both of which are
incorporated herein by reference. Load cell system 54 may also
monitor movement of the occupant of person support apparatus 20 in
other ways, including manners discussed in greater detail
below.
[0041] Load cells 52 are positioned generally adjacent each corner
of litter frame 28, as shown more clearly in FIG. 4. A head end set
of load cells 52a, 52b is coupled to a head end signal acquisition
node 56a by way of a pair of signal lines 82a and 82b. Signal lines
82a and 82b are wires, or other conventional communication media,
that forward the analog outputs of load cells 52a, 52b to head end
signal acquisition node 56a. A foot end set of load cells 52c, 52d
is coupled to a foot end signal acquisition node 56b by way of a
pair of signal lines 82c and 82d. Signal lines 82c and 82d, like
signal lines 82a and 82b, are wires, or other conventional
communication media, that forward the analog outputs of load cells
52c and 52d to foot end signal acquisition node 56b. Lines 82a-d
are therefore analog signal lines that couple together two sets of
load cells 52 to two signal acquisition nodes 56a and 56b.
[0042] Because lines 82a-d transmit analog signals, any
electromagnetic interference or electrostatic discharges within the
proximity of lines 82a-d are more likely to introduce errors into
the analog signals transmitted to signal acquisition nodes 56a and
56b along lines 82a-d than if these lines were transmitting digital
signals. In order to reduce such errors, signal acquisition node
56a is positioned generally midway between the head end set of load
cells 52a and 52b, thereby ensuring that the physical lengths of
lines 82a and 82b are as short as possible. These shortened lengths
reduce the ability of the lines 82a, 82b to act as antennas for
detecting electromagnetic interference and/or electrostatic
discharges. Accordingly, head end signal acquisition node 56a is
centered between load cells 52a and 52b in order to reduce the
susceptibility of lines 82a and 82b to noise.
[0043] Foot end signal acquisition node 56b is similarly positioned
at a location that is centered between foot end load cells 52c and
52d. As with head end signal acquisition node 56a, foot end signal
acquisition node 56bs position midway between its neighboring load
cells (52c and 52d) ensures that the physical length of lines 82c
and 82d is as short as possible. This shortened length reduces the
ability of the lines 82c, 82d to act as antennas for detecting
electromagnetic interference and/or electrostatic discharges.
Accordingly, foot end signal acquisition node 56b is centered
between load cells 52c and 52d in order to reduce the
susceptibility of lines 82c and 82d to noise.
[0044] Each signal acquisition node 56a and 56b communicates with
controller 58 via a communication line 84. Communication lines 84,
unlike signal lines 82, convey digital signals, rather than analog
signals. Accordingly, communication lines 84 are far less
susceptible to interference. As a result, the physical length of
lines 84 is generally immaterial and controller 58 can be
positioned at any suitable location on person support apparatus 20.
Controller 58 therefore can be moved from the position generally in
the center of person support apparatus 20, as shown in FIG. 4, to
any suitable location on person support apparatus 20. Indeed, in
some embodiments, controller 58 may be mounted on a common circuit
board on which one of signal acquisition nodes 56 is also mounted.
In other embodiments, each signal acquisition node 56 and
controller 58 is mounted on its own circuit board.
[0045] Although the composition of each signal acquisition node
56a, 56b may vary, FIG. 5 illustrates one illustrative embodiment
of implementing signal acquisition node 56a and/or 54b. As shown
therein, signal acquisition node 56 includes protection circuitry
64, one or more low pass filters and/or amplifiers 66, an
analog-to-digital converter 68, memory 70 in which one or more
algorithms are stored, a sensor network 72, a digital signal
processor 74, a diagnostics module 76, a power supply 78, and
communications circuitry 80.
[0046] Protection circuitry 64 (FIG. 5) includes one or more
circuits adapted to reduce noise caused by electromagnetic
interference (EMI) and/or electrostatic discharge (ESD) and to
reduce or prevent its interference with the proper operation of
load cells 52 and signal acquisition node 56. Low pass
filter/amplifier 66 filters and/or amplifies the outputs from each
load cell 52 that is fed into signal acquisition node 56 via signal
lines 82 (FIG. 4). The cutoff frequency of the low pass filtering
is chosen to remove high frequency components received from lines
82 that are due to noise and/or that represent signal components
that are unrelated to the scale, exit alert, and/or occupant
monitoring functions of load cell system 54.
[0047] In the illustrated embodiment, analog-to-digital (ND)
converter 68 is at least a two channel A/D converter wherein a
first channel converts the analog signals received from a first
load cell (e.g. 52a) to digital signals and a second channel
converts the analog signals from a second load cell (e.g. 52b) to
digital signals (FIG. 4). The digital signals output from each
channel of A/D converter 68 are then fed to digital signal
processor 74 for further processing. In some embodiments, two
separate single-channel ND converters 68 are used in place of a
single dual-channel ND converter 68. Regardless of the number of
channels and/or A/D converters 68, each ND converter is capable of
operating at different sampling rates. As will be discussed in
greater detail below, the sampling rate at which the ND converters
68 sample the analog signals received from lines 82 is varied by
load cell system 54. The changes to this sampling rate are carried
out, in at least one embodiment, by digital signal processor
74.
[0048] Memory 70 (FIG. 5) includes programming stored therein for
carrying out one or more algorithms executed by digital signal
processor 74. Such algorithms include algorithms for processing the
outputs from load cells 52, as well as, in at least some
embodiments, fusing the outputs from load cells 52 with the outputs
from one or more additional sensors that feed into signal
acquisition node 56. Such additional sensors may vary from
embodiment to embodiment. In some embodiments, the additional
sensors include one or more accelerometers adapted to detect
accelerations caused by movement of the occupant of person support
apparatus 20 while the occupant is positioned on support deck 30.
One example of such an accelerometer sensing system is disclosed in
commonly assigned U.S. patent application Ser. No. 62/253,167 filed
Nov. 10, 2015, by inventors Marko Kostic et al. and entitled PERSON
SUPPORT APPARATUSES WITH ACCELERATION DETECTION, the complete
disclosure of which is incorporated herein by reference.
[0049] Another type of sensor whose data may be fused with the
outputs from load cells 52 is a thermal image sensor adapted to
capture thermal images of the occupant of person support apparatus
20 while the occupant is supported on person support apparatus 20.
One example of a thermal imaging system with outputs suitable for
fusing with the outputs of load cells 52 is disclosed in U.S.
patent application Ser. No. 14/692,871 filed Apr. 22, 2015, by
inventors Marko Kostic et al. and entitled PERSON SUPPORT APPARATUS
WITH POSITION MONITORING, the complete disclosure of which is
incorporated herein by reference. Another type of sensor whose data
may be fused with the outputs from the load cells 52 is a sensor
that detects the presence/absence of a component of person support
apparatus 20 whose weight is detectable by load cell system 54. For
example, a sensor may be used to detect if footboard 34 is present
or not, or a headboard, or another component. Adjustments to the
taring and/or zeroing functions of the load cell system can be made
according to changes detected by these types of sensors. Still
other types of sensors may be used whose outputs are fused with the
outputs from load cells 52 and used for performing, or assisting in
the performance of, one or more of the scale, exit detection,
and/or occupant monitoring functions of load cell system 54.
[0050] Sensor network 72 (FIG. 5) refers to the load cells 52 that
are coupled to signal acquisition node 56 by way of signal lines
82, as well as any other additional sensors that have their outputs
fused together with the outputs of load cells 52.
[0051] Digital signal processor 74 (FIG. 5) is, in at least one
embodiment, a conventional microcontroller. It will be understood,
however, that digital signal processor 74 may take on other forms.
In general, digital signal processor 74 may include any one or more
microprocessors, microcontrollers, field programmable gate arrays,
systems on a chip, volatile or nonvolatile memory, discrete
circuitry, and/or other hardware, software, or firmware that is
capable of carrying out the functions described herein, as would be
known to one of ordinary skill in the art. Such components can be
physically configured in any suitable manner, such as by mounting
them to one or more circuit boards, or arranging them in other
manners, whether combined into a single unit or distributed across
multiple units. The instructions followed by digital signal
processor 74 when carrying out the functions described herein, as
well as the data necessary for carrying out these functions, are
stored in memory 70.
[0052] Diagnostic circuits 76 (FIG. 5) include one or more circuits
used by digital signal processor 74 for carrying out one or more
diagnostic functions associated with signal acquisition node 56. In
some embodiments, diagnostic circuits 76 include one or more of the
circuits disclosed in commonly assigned U.S. patent application
Ser. No. 15/185,623 filed Jun. 17, 2016, by inventors Marko Kostic
et al. and entitled PERSON SUPPORT APPARATUS WITH LOAD CELLS, the
complete disclosure of which is incorporated herein by reference.
Other types of diagnostic circuits can, of course, be used.
[0053] Power supply 78 (FIG. 5) includes circuitry for regulating
the electrical power supplied to signal acquisition node 56 and
load cells 52. Such circuitry 78 may include conventional
components and designs for regulating and supplying electrical
power, including, but not limited to, circuitry for rectifying
alternating current (AC) to direct current (DC) and/or circuitry
for changing the supplied voltage levels to voltage levels suitable
for the electrical components of load cell system 54.
[0054] Communications circuitry 80 (FIG. 5) provides communication
abilities to signal acquisition node 56 enabling it to communicate
with controller 58 over communication line 84 (FIG. 4). As noted
previously, communication lines 84 are digital communication lines
in the illustrated embodiment. This contrasts with signal lines 82,
which are analog. Communication lines 84 are, in at least one
embodiment, wired communication paths. Such wired communication may
be implemented using any of the following: a Controller Area
Network (CAN) bus, a Local Interconnect Network (LIN) bus,
Firewire, I-squared-C, RS-232, RS-485, a Universal Serial Bus
(USB), and/or a Serial Peripheral Interface (SPI) bus. Other types
of communication protocols may also be used, including wireless
communication.
[0055] Communications circuitry 80 includes transceivers and/or
other circuitry necessary for implementing the particular
communication protocol used by signal acquisition node 56. In some
embodiments, communication lines 84 may be Ethernet lines, such as
disclosed in commonly assigned U.S. patent application Ser. No.
14/622,221 filed Feb. 13, 2015, by inventors Krishna Bhimavarapu et
al. and entitled COMMUNICATION METHODS FOR PATIENT HANDLING
DEVICES, the complete disclosure of which is incorporated herein by
reference. In such instances, communication circuitry 80 includes
one or more Ethernet interfaces and/or magnetics for implementing
Ethernet communications with controller 58.
[0056] Controller 58 communicates with each signal acquisition node
56a, 56b, as well as communications module 60 and control panel 62
(FIG. 4). Communications module 60 includes one or more
transceivers that communicate with one or more off-board devices.
In one embodiment, module 60 includes a WiFi radio adapted to
communicate with wireless access points of a healthcare facility's
computer network, thereby enabling the person support apparatus 20
to communicate wirelessly with the computer network of the
healthcare facility. Module 60 may also or alternatively include an
Ethernet connection, or other wired circuitry, for enabling wired
communication with the hospital network, as well as nurse call
cable circuitry for coupling to a nurse call cable that
communicates with a nurse call system of a healthcare facility.
[0057] Controller 58, as with digital signal processors 74, is a
microcontroller, in at least one embodiment. In other embodiments,
controller 58 may include any one or more microprocessors,
microcontrollers, field programmable gate arrays, systems on a
chip, volatile or nonvolatile memory, discrete circuitry, and/or
other hardware, software, or firmware that is capable of carrying
out the functions described herein, as would be known to one of
ordinary skill in the art. Such components can be physically
configured in any suitable manner, such as by mounting them to one
or more circuit boards, or arranging them in other manners, whether
combined into a single unit or distributed across multiple units.
The instructions followed by controller 58 in carrying out the
functions described herein, as well as the data necessary for
carrying out these functions, are stored in a memory (not labeled)
accessible to controller 58.
[0058] The analog outputs from load cells 52 are passed via lines
82 to signal acquisition nodes 56a and 56b (FIG. 4). After having
high frequency components removed via low pass filters/amplifiers
66, each signal acquisition node 56 converts the analog signals
received via line 82 into digital signals using analog-to-digital
converters 68. In addition to converting the analog load cell
signals into digital signals, each signal acquisition node 56 also
scales the outputs from the individual load cells 52 and/or
calibrates the outputs from each load cell 52. This scaling and/or
calibration is performed by signal processor 74 of each signal
acquisition node 56 and is based, at least partly, upon individual
characteristics of each load cell 52. After the digitized outputs
from each load cell have been processed by signal processor 74,
they are transmitted via communications circuitry 80 over
communication lines 84 to controller 58. As mentioned previously,
in some embodiments, one or more additional sensors feed their
outputs into signal acquisition nodes 56. In those embodiments, the
outputs from the additional sensors are digitized, scaled,
calibrated, and/or otherwise processed by signal processor 74
before being transmitted over lines 84 to controller 58.
[0059] The data that is transmitted over line 84 to controller 58
is time stamped, or otherwise indexed, so that controller 58 is
able to match the data received from head end signal acquisition
node 56a with the data received from foot end signal acquisition
node 56b. In other words, the messages transmitted over lines 84 to
controller 58 include a time stamp or other type of indexing
feature to allow controller 58 to match the readings from load
cells 52a and 52b that were taken at time X with the readings from
load cells 52c and 52d that were also taken at time X (or, in some
cases, the readings from load cells 52c and 52d that were taken at
a time that most closely matches time X). If data from other
sensors is also forwarded to controller 58, such time stamping or
indexing features may also be sent with that data as well.
[0060] Controller 58 processes the data from signal acquisition
nodes 56 in different manners depending upon how load cell system
54 is being used at a given time. As noted previously, load cell
system 54 may be used as a scale, as an exit detection system,
and/or as an occupant monitoring system. Control panel 62 includes
a scale control 86a (FIG. 4) that is selectable by a user of person
support apparatus 20. When the scale control 86a is selected,
controller 58 processes the load cell data from signal acquisition
nodes in a manner that yields an accurate weight of the occupant.
This is accomplished by summing the measurements from all of the
load cells 52 that were taken at the same time, or substantially
the same time. Multiple measurements may be used in some
embodiments that are then averaged or otherwise combined.
[0061] Control panel 62 also includes an exit detection control 86b
(FIG. 4) that, when selected, arms an exit detection system. When
the exit detection system is armed, controller 58 processes the
data from signal acquisition nodes 56 to determine if the occupant
is moving in a manner suggestive of an impending exit from person
support apparatus 20, and/or to determine if the occupant has
exited from person support apparatus 20. If either condition is
present, controller 58 issues an alert, which may be both local to
person support apparatus 20 and/or remote to person support
apparatus 20 (the remote alert is accomplished by sending an alert
message to a remote device via communications module 60).
[0062] When the exit detection system is armed, controller 58
determines if the occupant is about to exit, or already has exited,
from person support apparatus 20 by computing a center of gravity
of the occupant of person support apparatus 20 using the digital
data supplied by signal acquisition nodes 56, and then comparing
the center of gravity to one or more zones or other boundary
criteria. Alternatively, controller 58 determines if the occupant
is about to exit, or already has exited, from person support
apparatus 20 by determining a distribution of the weights detected
by each load cell 52 and comparing the detected weight distribution
to one or more thresholds. The weight distribution uniquely
identifies the center of gravity whether the center of gravity is
explicitly calculated or not.
[0063] In some embodiments, person support apparatus 20 does not
include an occupant monitoring control. Instead, controller 58 is
adapted to automatically monitor the movement of the occupant
whenever person support apparatus 20 is powered, or automatically
monitor the movement of the occupant based on one or more other
conditions. In other embodiments, control panel 62 may include an
occupant monitoring control (e.g. control 86c of FIG. 4) that
allows a user to selectively start and stop the occupant monitoring
function. The occupant monitoring function includes monitoring
whether the occupant is present or absent on person support
apparatus 20, keeping track of the times when the occupant exits
from, and returns to, person support apparatus 20, and, in some
embodiments, tracking the movement of the occupant when he or she
is present on person support apparatus 20.
[0064] Further, in some embodiments, as will be discussed in
greater detail below, the occupant monitoring function also
includes an automatic taring function that automatically calculates
a tare weight reading. The tare weight reading is stored in memory
and used to automatically compute the weight of the occupant after
he or she enters or leaves person support apparatus 20. Tare weight
readings may also be determined automatically at other times in
order to detect and determine the changes in weight associated with
the addition and removal of objects from person support apparatus
20. The tare weight readings are used in some embodiments to
distinguish the weight of the occupant of person support apparatus
20 from the weight of non-patient items, such as the physical
components of support deck 30, litter frame 28, bedding, pillows,
etc. By knowing the tare weight, controller 58 is able to
automatically zero the scale system by subtracting the tare weight
from the current weight reading. If the occupant is absent from
person support apparatus 20, the result of this subtraction is
zero. If the occupant is present, the result of this subtraction is
the patient's weight.
[0065] Still further, in some embodiments, the occupant monitoring
function includes monitoring one or more of the occupant's vital
signs when supported on person support apparatus 20. Alternatively,
control panel 62 may include a separate vital signs monitoring
control that, when activated, instructs load cell system to start
or stop monitoring one or more vital signs of the occupant. In some
embodiments, the vital signs include the occupant's breathing rate
and heart rate. The monitoring of the occupant's heart rate is made
possible by the forces transferred onto support deck 30 from the
occupant's heartbeat, which are detectable by load cells 52.
Similarly, the monitoring of the occupant's breathing is made
possible by the forces transferred onto support deck 30 from the
expansion and contraction of the occupant's chest cavity as he or
she breathes, and these forces are also detectable by load cells
52. Illustrative manners of detecting a person's heart rate and
breathing rate that may be used with any of the load cell systems
disclosed herein are disclosed in commonly assigned U.S. Pat. No.
7,699,784 issued Apr. 20, 2010, to David Wan Fong et al. and
entitled SYSTEM FOR DETECTING AND MONITORING VITAL SIGNS, the
complete disclosure of which is incorporated herein by reference.
The detection of the occupant's vital signs using load cells 52 may
be augmented, or supplanted, with any of the methods disclosed in
commonly assigned U.S. patent application Ser. No. 62/253,167,
which has previously been incorporated herein by reference.
[0066] In the embodiment illustrated in FIG. 4, when a user selects
the scale control 86a, controller 58 sends a message along lines 84
to each of the signal acquisition nodes 56 informing them that the
user has selected the scale function. In response to this message,
each digital signal processor 74 sends a control signal to its
associated A/D converter 68 causing the A/D converter to switch
from a higher sampling rate to a lower sampling rate. To the extent
the ND converter 68 was already operating at a lower sampling rate
(as will be discussed more below), A/D converter 68 continues to
operate at the lower sampling rate until a control signal is
subsequently received from digital signal processor 74 causing it
to change sampling rates.
[0067] The values of the higher and lower sampling rates may vary,
depending upon the design of the specific A/D converter 68 used,
the circuitry of load cell system 54, the desired range of
frequencies to be detected by load cells 52, and/or other factors.
In one embodiment, the lower sampling rate refers to a sampling
rate of 1 to 100 Hertz, and the higher sampling rate refers to a
sampling rate of approximately 1000 Hertz or more. Other sampling
rate ranges, however, can be used for the higher and lower sampling
rates. In some embodiments, any ranges may be used where the higher
sampling rate is ten or more times as fast as the lower sampling
rate. Still further, in some embodiments, controller 58 is
configured to select between more than two sampling rates, thereby
instructing the ND converters 68 to operate at at least three
different sampling rates, depending upon the particular function
being carried out by load cell system 54 at that time.
[0068] The different sampling rates used by A/D converters 68
result in different levels of accuracy of the digitized outputs
from the A/D converters 68, as would be known to a person of
ordinary skill in the art. When an A/D converter is operating at a
higher sampling rate, the accuracy of the digitized outputs are
lower than when the A/D converter is operating at a lower sampling
rate. Operating at a lower sampling rate, however, reduces the
ability of the A/D converter to detect oscillations in the load
cell outputs. As is known from the Nyquist-Shannon sampling
theorem, the A/D converters 68 cannot accurately reproduce signals
from the load cells that oscillate at frequencies greater than half
the frequency of their sampling rates. Accordingly, controller 58
generally switches the sampling rates of A/D converters 68 between
the two sampling rates depending upon the changing functions of
load cell system 54, i.e. whether load cell system 54 is being used
in a manner where accuracy of weight is desired or whether load
cell system 54 is being used in a manner where it is desirable to
detect load cell oscillations having frequencies of more than half
the sampling rate that aren't otherwise detectable without
aliasing.
[0069] As noted previously, when a user selects the scale function
using the scale control 86a, controller 58 sends a message to the
signal acquisition nodes 56 instructing them to switch their A/D
converters 68 to a lower sampling rate. This lower sampling rate
continues for as long as it takes to obtain a successful weight
reading. In some embodiments, the outputs from each of the load
cells 52 is summed together multiple times while the A/D converters
68 are operating at the low sampling rate and the multiple sums are
averaged. Controller 58 reports this average to control panel 62,
in at least some embodiments.
[0070] In some embodiments, after the weight reading has been
taken, signal acquisition nodes 56 automatically switch their
respective A/D converters 68 back to their fast sampling rates.
This automatic switching occurs when person support apparatus 20 is
configured to automatically revert to the occupant monitoring
function (in the absence of a user actively selecting the scale
control 86a or the exit detection control 86b). If person support
apparatus 20 is not configured to automatically revert to
performing the occupant monitoring function when the scale function
and/or exit detection functions are not active, controller 58 may
continue to have ND converters 68 process the load cell outputs at
a slow sampling rate until a user takes an action, or an event
occurs, that prompts controller 58 to instruct A/D converter 68 to
switch to faster sampling rate.
[0071] When a user selects the exit detection control 86b on
control panel 62 to activate the exit detection function (i.e. arm
the exit detection system), controller 58 changes the sampling rate
of A/D converters 68 in different manners, depending upon what
other functions are being carried out by load cell system 54 at
that time. For example, it is possible to simultaneously activate
both the scale function and the exit detection function. If the
scale function is activated at the same time the exit detection
function is activated, controller 58 instructs A/D converters 68 to
take samples at a slow rate. If the scale function is not activated
and the exit detection function is activated, controller 58
instructs A/D converters 68 (via digital signal processors 74 of
signal acquisition nodes 56) to take samples at the faster rate. If
neither the scale control 86a nor the exit detection control 86b is
activated, controller 58 instructs A/D converters 68 to take
samples at the fast rate.
[0072] In at least one embodiment, controller 58 instructs the ND
converters 68 to take samples at the slower rate when scale control
86a is activated, and controls the sampling rates of the ND
converters 68 at other times based upon the outputs of the load
cells. In such embodiments, some of which are discussed in greater
detail below with respect to FIGS. 8 and 9, the sampling rate of
the A/D converters 68 may vary automatically during time periods
when the exit detection control 86b has been activated, and may
also vary automatically during time periods when neither the exit
detection control 86b nor the scale control 86a have been
activated, such as when the occupant monitoring function is taking
place. Still further, in some embodiments, such as, but not limited
to, those embodiments where a patient's vital signs are being
monitored, controller 58 may be configured to automatically switch
to the faster sampling rate at all times when an accurate weight
reading is not needed.
[0073] FIG. 6 depicts an alternative load cell system 54a that may
be used with person support apparatus 20. Those components of load
cell system 54a that are common to load cell system 54 are numbered
with the same reference numbers. Those components of load cell
system 54a that are not found in load cell system 54, or that are
modified from load cell system 54, are provided with a new or
modified reference number and described in more detail below. Load
cell system 54a is adapted to implement and perform any or all of
the functions described above with respect to load cell system 54.
These include, but are not limited to, performing a scale function,
acting as an exit detection system, monitoring movement of the
occupant (including gross movement and/or shivering), and
monitoring one or more vital signs of the occupant.
[0074] One of the differences between load cell system 54a and load
cell system 54 is the addition of a communications channel 90
directly between head end signal acquisition node 56a and foot end
signal acquisition node 56b. Channel 90 is a digital communications
channel that may be implemented in any of the various manners
described above with respect to communication lines 84 (e.g. a CAN
bus, a LIN bus, Firewire, I-squared-C, RS-232, RS-485, USB, an SPI
bus, Ethernet, etc.). Foot end signal acquisition node 56b sends
the digitized, filtered, and (in some cases) processed outputs from
load cells 52c and 52d to head end signal acquisition node 56a via
communication channel 90, unlike signal acquisition node 56b of
load cell system 54, which sends this information directly to
controller 58. Digital signal processor 74 of head end signal
acquisition node 56a uses the signals from foot end signal
acquisition node 56b to compute the detected weight, movement,
and/or vital signs of the occupant of person support apparatus 20.
The computed outputs are then forwarded to controller 58 which
takes one or more steps in response (e.g. displaying information
from load cell system 54a on a display of control panel 62,
forwarding information from load cell system 54a to another device
via communications module 60, etc.).
[0075] Head end signal acquisition node 56a computes a detected
weight, movement (including, but not limited to, movement
indicative of an exit from person support apparatus 20), and/or
vital signs of the occupant in any of the manners previously
described with respect to controller 58 and load cell system 54. In
performing these calculations, head end signal acquisition node 56a
changes the sampling rate of its A/D converter 68 and sends
commands via channel 90 to the A/D converter 68 of foot end signal
acquisition node 56b to change its sampling rate. The changes to
the sampling rates are carried out in accordance with any of the
algorithms described above with respect to load cell system 54
(e.g. switching to a slow rate when weighing the occupant,
switching to a faster rate when detecting vital signs, shivering,
and/or movement, etc.).
[0076] Load cell system 54a thus differs from load cell system 54
primarily in that the computational burden of processing the
outputs from the two signal acquisition nodes 56a and 56b is
offloaded from controller 58 to the digital signal processor 74 of
head end signal acquisition node 56a. It will, of course, be
understood by those skilled in the art that load cell system 54a
may be modified so that the computational burden is offloaded to
digital signal processor 74 of foot end signal acquisition node 56b
instead. In this modified embodiment, head end signal acquisition
node 56a sends the digitized outputs from load cells 52a and 52b
over channel 90 to foot end signal acquisition node 56b for
processing. Foot end signal acquisition node 56b thereafter shares
the processed results with controller 58 via a communication line
84 that extends therebetween (not shown in FIG. 6).
[0077] FIG. 7 depicts another alternative load cell system 54b that
may be used with person support apparatus 20. Those components of
load cell system 54b that are common to load cell systems 54 and/or
54a are numbered with the same reference numbers. Those components
of load cell system 54b that are not found in load cell systems 54
or 54a, or that are modified from load cell systems 54 or 54a, are
provided with a new or modified reference number and described in
more detail below. Load cell system 54b is adapted to implement and
perform any or all of the functions described above with respect to
load cell systems 54 and 54a. These include, but are not limited
to, performing a scale function, acting as an exit detection
system, monitoring movement of the occupant, monitoring one or more
vital signs of the occupant, and in some instances, detecting
shivering by the occupant.
[0078] Load cell system 54b includes a communication channel 90
that communicatively couples head end and foot end signal
acquisition nodes 56a and 56b together. Unlike load cell system 54a
where one of the nodes 56a, 56b sends its digitized outputs to the
other node, both of the nodes 56a and 56b send their digitized data
to each other. That is, each signal acquisition node 56a and 56b
processes the outputs from its own two connected load cells 52
(received on signal lines 82) as well as the outputs from the other
two load cells that are connected to the other signal acquisition
node (received via communication channel 90). Signal acquisition
nodes 56a and 56b therefore perform redundant processing. This is
done in order to guard against failure of the entire load cell
system 54b if either signal acquisition node 56 or 56b individually
fails. This helps ensure that load cells system 54b continues to
operate properly in the face of a single signal acquisition node
failure.
[0079] In order to fully implement this redundancy, load cell
system 54b further includes a second communication line 84a that
extends between foot end signal acquisition node 56b and controller
58. The outputs from all four load cells 52a-d that are processed
by signal acquisition node 56a are sent to controller 58 via
communication line 84 while the outputs from all four load cells
52a-d that are processed by signal acquisition node 56b are sent to
controller 58 via communication line 84a. Communication lines 84
and 84a therefore provide redundant communication pathways that
allow the continued operation of load cell system 54b in the event
of the failure of one of these. In at least one embodiment,
controller 58 is programmed to select one of the sets of redundant
outputs (from nodes 56a or 56b) for further processing, display,
and/or forwarding. In the event one set of these redundant outputs
fails, controller 58 switches to using the other set of redundant
outputs.
[0080] FIG. 8 depicts a graph 92 of the gross weight sensed by load
cells 52 over a time period in which an occupant enters person
support apparatus 20. This graph illustrates one manner in which
any of load cell systems 54, 54a, and/or 54b may implement an
automatic-zeroing function that renders it unnecessary to manually
zero the scale prior to the occupant entering person support
apparatus 20. The automatic-zeroing function not only zeroes the
scale reading with respect to the weight present on person support
apparatus 20 prior to the occupant entering person support
apparatus 20, but also automatically zeros the scale reading while
the occupant is supported on person support apparatus 20 and
objects are added to, or removed from, person support apparatus 20.
Further, as will be discussed in greater detail below, this graph
illustrates one manner in which transitions between the slow and
fast sampling rates of A/D converters 68 may be carried out.
[0081] As shown in FIG. 8, during an initial time period 94, the
gross weight 96 detected by the load cells 52a-d remains generally
steady. While this gross weight is generally steady, controller 58
(or digital signal processors 74 of signal acquisition nodes 56a,
56b) instructs A/D converters 68 to periodically take readings at a
low sampling rate. As shown in FIG. 8, the low sampling rate
readings occur during short periods of time that are labeled A.
These short periods of time may last for a few seconds, or for
different lengths of time. During these short periods of time, one
or more readings from the load cells 52 are taken using the low
sampling rate of the A/D converters. These one or more readings are
used to generate an accurate reading of the gross weight detected
by the load cells 52 during these time periods A. This accurate
weight reading is a tare weight reading and is indicated by the
letter T in FIG. 8. This value is stored in a memory of person
support apparatus 20 and used later when calculating a weight of an
occupant, as discussed in greater detail below. In between the time
periods labeled A in FIG. 8, readings from the A/D converters are
taken at a fast sampling rate, as will be discussed more below.
[0082] It will be understood that the initial time period 94 shown
in FIG. 8 is of an arbitrary length that may vary in actual
practice. However long or short the actual length of initial time
period 94, the tare value T is determined from outputs of the load
cells 52 using digitized samples gathered during one or more of the
slow sampling rate time periods labeled A (which yield more
accurate results). The initial time period transitions into an
intermediate time period 98 when a change in the gross weight 96 is
detected that is greater than a predefined threshold. If this
change occurs during a time period A, it prompts load cell systems
54, 54a, and/or 54b to switch the sampling rates of the A/D
converters to the fast sampling rate. If this change occurs between
time periods A when a fast sampling rate is already in use, the
fast sampling rate continues to be used. In either case, the fast
sampling rate is used to take readings from the load cells 52
throughout the intermediate time period 98.
[0083] The intermediate time period 98 comes to an end when the
amount of variation in the gross weight stabilizes (i.e. falls
below a threshold for more than a threshold amount of time). Once
intermediate time period 98 ends, load cell system 54, 54a, and/or
54b periodically switches its A/D converter sampling rates back to
the slow rates for the brief amounts of time labeled A. In between
time periods A of subsequent time period 100, the A/D converters
are switched back to their high sampling rate. During at least one
of the time periods A of the subsequent time period 100, the load
cell system determines a gross weight value P. This represents the
gross weight detected by the load cell system after the occupant
has entered person support apparatus 20. The load cell system (54,
54a, or 54b) thereafter automatically determines the occupant's
weight by subtracting the tare weight T from the gross weight value
P. The particular component of the load cell system 54, 54a, or 54b
that performs these calculations may vary in these systems between
controller 58 and the digital signal processors 74 of the signal
acquisition nodes 56a, 56b.
[0084] The load cell system concludes that the weight that was
added to person support apparatus 20 during the intermediate time
period 98 is that of an occupant if the difference between the tare
weight T and the gross weight value P is greater than a threshold
S. If this difference is less than the value of the threshold S,
then the load cell system concludes that the added weight
corresponds to an object having been added to person support
apparatus 20, rather than an occupant. Because the load cell system
automatically determines the tare weight T prior to the occupant
entering person support apparatus 20, it is not necessary for the
user to manually activate a taring or zeroing function prior to the
occupant entering person support apparatus 20, as in some prior art
person support apparatuses.
[0085] In some embodiments, the load cell system is configured to
also utilize other data when distinguishing between animate and
inanimate objects being added to person support apparatus 20. For
example, in some embodiments, the load cell system looks for the
presence of vital signs during subsequent time period 100 (and in
some cases, during initial time period 96 as well). If vital signs
are detected, the load cell system concludes that an occupant has
entered person support apparatus 20, even if the aforementioned
weight difference is less than S. Alternatively, if no vital signs
are detected, the load cell system concludes that no occupant has
entered person support apparatus 20, even if the aforementioned
weight difference exceeds the value S.
[0086] In some embodiments, controller 58 and/or one or more signal
acquisition nodes 56 of load cell systems 54, 54a, and/or 54b are
configured to compare outputs from the load cells 52 both during
initial time period 94 and subsequent time period 100. In such
embodiments, if vital signs are detected during initial time period
94, the load cell system concludes that an inanimate object has
been added during the intermediate period, even if the object has a
weight greater than threshold S. If vital signs are not detected
during initial time period 94, but are detected during subsequent
time period 100, the load cell system concludes that an occupant
has entered person support apparatus. If vital signs are not
detected during either initial time period 94 or subsequent time
period 100, the load cell system concludes that an inanimate object
was added to person support apparatus 20, regardless of whether the
object's weight exceeds threshold S or not. Other conclusions
and/or algorithms for using the vital signs may be incorporated
into any of the load cell systems 54, 54a, and/or 54b.
[0087] Still further, either in addition to, or in lieu of, using
vital signs to distinguish between animate and inanimate objects
positioned on person support apparatus 20, any of the load cell
systems 54, 54a, and/or 54b may look at changes in the center of
gravity or mass distribution that exceed a threshold. If movement
that is greater than a threshold is detected on the person support
apparatus 20 after weight has been added or removed, this is
indicative of person support apparatus being occupied by a person.
If the previous weight change was a reduction in weight, then the
reduction was likely due to an inanimate object being removed. If
the previous weight change was an addition in weight, then the
addition in weight was likely due to the person entering person
support apparatus 20 (if the added weight was large enough to
signify a person and/or no movement was detected prior to that
weight addition), or it was likely due to an inanimate object being
added (if the added weight was not large enough to signify a person
and/or movement was detected prior to the weight addition). In
addition to movement, the load cell system may also or
alternatively look at the location of the added or removed weight
to distinguish animate from inanimate objects. Occupants will tend
to have their weight more centered while inanimate objects will
tend to be added peripherally. Methods for monitoring the movement
and/or location of added and removed weights are disclosed in more
detail in commonly assigned U.S. patent application Ser. No.
14/873,734 filed Oct. 2, 2015, by inventors Marko Kostic et al. and
entitled PERSON SUPPORT APPARATUS WITH MOTION MONITORING, the
complete disclosure of which has already been incorporated herein
by reference.
[0088] FIG. 9 depicts a graph 92a of the gross weight 96 sensed by
load cells 52 over a time period in which both an inanimate object
has been placed on person support apparatus 20 and the occupant has
entered person support apparatus 20. This graph illustrates one
manner in which any of load cell systems 54, 54a, and/or 54b may
implement an automatic-zeroing function as well an automatic
accounting of objects placed on person support apparatus 20. Graph
92a also illustrates a manner for transitioning between the slow
and fast sampling rates of ND converters 68.
[0089] As shown in FIG. 9, the load cell system (54, 54a, and/or
54b) calculates a tare weight T during an initial time period 94.
This tare weight is labeled T1 in FIG. 9. The tare weight T1 is
calculated during one or more of the slow sampling rate periods of
time that are labeled A. Between these time periods A, readings are
taken at the fast sampling rate. When a change in the load cell
outputs (gross weight 96) is detected that exceeds a threshold,
intermediate time period 98 commences and--if a fast sampling rate
is not already being used--the sampling rate is switched to the
high sampling rate. The high sampling rate continues through the
intermediate time period 100.
[0090] After the changes in the gross weight subside below a
threshold amount, intermediate time period 100 comes to an end, and
the sampling rate is periodically switched back to a slow rate for
short time periods A during subsequent time period 100. During one
or more of these short time periods A of subsequent time period
100, the load cell system determines the gross weight, which in
FIG. 9 is labeled T2. After T2 is determined, the load cell system
subtracts T1 from T2 and compares this difference to the threshold
S. Because this difference is less than the threshold S, the load
cell system concludes that the weight that was added to the person
support apparatus 20 during the intermediate time period 98
corresponds to an inanimate object, not the occupant.
[0091] During subsequent time period 100, the load cell system
continues to monitor the gross weight reading 96 to look for
changes that exceed a threshold magnitude and/or time. When such a
change is detected, second intermediate time period 98a commences,
as shown in FIG. 9. During this time period 98a, to the extent
readings are not already being taken at the fast sampling rate, the
load cell system switches to the fast sampling rate and continues
to take readings at the fast sampling rate until the load cell
readings settle. When the changes subside (i.e. the settling
occurs), second intermediate period 98a ends and second subsequent
time period 100a begins. During second subsequent time period 100a,
the sampling rate of the A/D converters 68 is periodically switched
back to the slow rate for brief periods of time A during which one
or more gross weight readings are taken. These gross weight
readings are identified by the letter P in FIG. 9. The load cell
system subtracts the previous tare weight T2 from P and compares
the resulting difference to threshold S. Because this difference
exceeds S in this case, the load cell system concludes that the
weight added to person support apparatus 20 during second
intermediate time period 98a corresponds to an occupant.
[0092] Although not illustrated in FIG. 9 (or FIG. 8), the load
cell system processes the removal of objects from person support
apparatus 20 and the exit of the occupant from person support
apparatus 20 in the same manner. That is, the load cell system
determines the difference between the gross weight readings 96
after an intermediate period (e.g. 98, 98a, 98b, etc.) and the
gross weight readings 96 immediately prior to that intermediate
time period. The difference is then compared to the threshold. If
the removed weight is greater than S, the load cell system
concludes that the occupant has departed. If the removed weight is
less than S, the load cell system concludes that an inanimate
object has been removed from the person support apparatus 20.
[0093] For both FIGS. 8 and 9, the load cell system continues to
monitor the gross weight 96 readings after subsequent time period
100 in FIG. 8 and the second subsequent time period 100a in FIG. 9.
The continued monitoring is carried out in the same manner as
previously described. That is, any changes in the gross weight
reading that exceed a threshold magnitude and/or threshold time
cause the system to switch to the fast sampling rate (if not
already operating at the fast sampling rate). After such
transitions settle (e.g. intermediate time periods 98a, 98b, etc.)
the load cell system switches back to intermittently taking
readings during brief time periods A using the slow sampling rate,
and returning to the high sampling rate between time periods A. One
or more of the readings taken during a time period A are used to
calculates a gross weight. The control system compares the gross
weight to the immediately prior tare weight and determines if the
weight added (or subtracted) during the transition corresponds to a
person or an inanimate object.
[0094] The load cell system (54, 54a, and/or 54b) keeps a record of
the time at which all inanimate objects are added to, or removed
from, person support apparatus 20, as well as a record of the time
at which the occupant enters and leaves person support apparatus
20. Further, in some embodiments, the load cell system also
calculates a total amount of time that the occupant has been on
person support apparatus 20 and/or a total amount of time the
occupant has been off of person support apparatus 20. These values
are displayed on a display of control panel 62. This information
gives a caregiver associated with the occupant of person support
apparatus 20 an easily understandable measure of the mobility of
the occupant. The caregiver is thus informed of how active or
inactive the occupant of person support apparatus 20 is, and can
take follow up steps, as appropriate, to encourage more activity of
the occupant, particularly in cases where the occupant is a patient
whose recovery will likely be hastened by increased physical
activity.
[0095] In some embodiments, the load cell system is adapted to
display a ratio of the amount of total amount of time the occupant
has spent in person support apparatus 20 versus the total amount of
time the occupant has spent out of person support apparatus 20, or
vice versa. The ratio may be displayed over any desired time
period. For example, the ratio may be calculated based upon the
occupant's presence and absence from person support apparatus 20
over the last 24 hours, the last 48 hours, since the occupant first
starting using person support apparatus 20, or some other time
period. Control panel 62 is configured, in some embodiments, to
allow a user to select the time period over which the ratio is
calculated.
[0096] Still further, in some embodiments, person support apparatus
20 is configured to detect whether the occupant is asleep or not
when supported on person support apparatus 20. One suitable manner
for making this determination is disclosed in commonly assigned
U.S. patent application Ser. No. 14/776,842 filed Sep. 15, 2015, by
inventors Michael Hayes et al. and entitled PERSON SUPPORT
APPARATUS WITH PATIENT INFORMATION SENSORS, the complete disclosure
of which is incorporated herein by reference. In these embodiments,
the load cell system 54, 54a, and/or 54b may be configured to
calculate the ratio of the occupant's absence from and presence on
person support apparatus 20 (or vice versa) for only those time
periods during which the occupant is awake. In other words, the
load cell system may provide the user with a measurement of how
much of the occupant's waking hours he or she has spent on person
support apparatus 20 versus how much of the occupant's waking hours
he or she has spent off of person support apparatus 20. Still other
manners of displaying the record of the occupant's absence/presence
on person support apparatus 20, as well as the record of objects
added and removed from person support apparatus 20, may be
implemented.
[0097] In some embodiments of load cell systems 54, 54a, and/or
54b, once a steady state value of the gross weight 96 has been
achieved in the initial or subsequent time periods 94 or 100 (FIGS.
8 and 9) and a slow sampling rate has been used to take an accurate
weight reading during a time period A, the load cell system may
switch back to the fast sampling rate and remain there until one or
more events occur. In other words, instead of having time periods A
occur periodically, time periods A can be modified to be aperiodic.
Such events may include threshold-exceeding changes that occur over
time in the readings taken at the high sampling rate, user inputs,
and/or other events. Regardless of the trigger for switching back
to the low sampling rate, the low sampling rate periods of time A
allow more accurate weight readings to be taken. Conversely, when
using the faster sampling rate, the load cell system may be better
able to detect frequencies in the gross weight readings that are
not otherwise detectable by the slow sampling rate. Such
frequencies may correspond to the occupant's breathing, heart beat,
or shivering, or to vibrations from a medical device or equipment
positioned on or near person support apparatus 20, and/or from
other sources.
[0098] In some embodiments of load cell system 54, 54a, and/or 54b,
controller 58 and/or one or both of signal acquisition nodes 56a,
56b are configured to filter frequencies detected in the outputs of
load cells 52 that are above a cutoff frequency. In those
embodiments where the occupant's vital signs are detected, the
cutoff frequency is selected to be higher than the highest expected
vital sign. As one example, a person's heart rate might not be
expected to rise above 150-200 beats per minute, in which case a
cutoff frequency might be selected at somewhere between 300-400
Hertz, or something slightly above this range. By filtering out
such frequencies, the components of the load cell outputs that are
due to higher frequency vibrations are removed. As noted
previously, such vibrations may result from medical equipment
and/or devices that are positioned on or near person support
apparatus 20, or from other sources.
[0099] In any of the embodiments of load cell systems 54, 54a, and
54b, one or more additional hardware lines may be added between
controller 58 and the signal acquisition nodes 56a, 56b, and/or
between the two signal acquisition nodes 56a, 56b. Over such
hardware lines, the signal acquisition nodes 56a, 56b, and/or
controller 58 may transmit a square wave, or other type of periodic
signal. If this signal is not detected by the receiving structure
(e.g. one of nodes 56a, 56b, or controller 58), this provides an
indication of a fault in the transmitting structure. A sounding
device (e.g. a buzzer) is coupled to the hardware line by a switch,
or other structure, that closes in the absence of the periodic
signal from the hardware line, thereby activating the sounder. The
activation of the sounder provides an indication to the user of a
fault in the load cell system. This method of notifying the user of
a fault is entirely hardware implemented, and therefore continues
to provide a notification to the user even in the presence of a
software or processor fault with any of controller 58 and/or nodes
56a, 56b. Such a hardware-designed sounding devices helps ensure
users that, in the absence of the activation of the sounding
device, the load cell system is continuing to operate properly,
which is desirable when the load cell system is being used to
implement one or more safety-important functions (e.g. detecting
patient exit, vital signs, shivering, etc.).
[0100] When load cell system 54, 54a, and/or 54b is being used to
detect shivering of the occupant of person support apparatus 20,
controller 58 is configured in some embodiments to send a message
to an external device when the presence of shivering is detected.
In some of these embodiments, the external device is a thermal
control unit of the type disclosed in commonly assigned U.S. patent
application Ser. No. 62/425,813 filed Nov. 23, 2016, by inventors
Gregory Taylor et al. and entitled THERMAL SYSTEM, the complete
disclosure of which is incorporated herein by reference. In such
embodiments, the thermal control unit uses the shivering message
from controller 58 of person support apparatus 20 as a confirmation
of the detection of shivering by the thermal control unit. That is,
the thermal control unit includes its own shivering sensors, but
does not provide a shivering alarm to a user unless the shivering
is detected by multiple sensors, such as those of the load cell
system of person support apparatus 20 and one or more of the
shivering sensors coupled to the thermal control unit. Alternative
manners of processing the shivering message from person support
apparatus 20 may be implemented.
[0101] Control panel 62, in addition to controlling various aspects
of load cell systems 54, 54a, and 54b, may also include controls
for controlling other aspects of person support apparatus 20 (e.g.
motion). The control of these other functions may be carried out by
controller 58, or they may be carried out by one or more other
controllers that that are in communication with motors or other
components that are controllable by control panel 62.
[0102] Various additional alterations and changes beyond those
already mentioned herein can be made to the above-described
embodiments. This disclosure is presented for illustrative purposes
and should not be interpreted as an exhaustive description of all
embodiments or to limit the scope of the claims to the specific
elements illustrated or described in connection with these
embodiments. For example, and without limitation, any individual
element(s) of the described embodiments may be replaced by
alternative elements that provide substantially similar
functionality or otherwise provide adequate operation. This
includes, for example, presently known alternative elements, such
as those that might be currently known to one skilled in the art,
and alternative elements that may be developed in the future, such
as those that one skilled in the art might, upon development,
recognize as an alternative. Any reference to claim elements in the
singular, for example, using the articles "a," "an," "the" or
"said," is not to be construed as limiting the element to the
singular.
* * * * *